Softly does it

Published in the leading journal Nature Chemistry, recent work by Ben Gardner, a postdoctoral researcher in the research group led by Prof. Steve Liddle, has reported the first examples of uranium with covalent single, double, and triple bonds to arsenic.

Nuclear power could produce far less carbon dioxide than fossil fuels, but the waste it produces is potentially some of the most dangerous in the world. In order to find ways of separating, recycling and reducing nuclear waste, research has focussed on developing our understanding of how uranium interacts with elements from around the periodic table to potentially help improve the selective extraction of spent uranium in nuclear waste clean-up.

Prof. Liddle said: “We need to reduce the volume of nuclear waste to make it easier to handle, and process it to remove benign elements or separate the high level waste from low level waste. This latest study looked at how soft elements such as arsenic interact with uranium – arsenic could in principle be used in organic molecules that bond to metal atoms and improve extraction processes.

There is currently a lot of interest in using organic molecules to extract, selectively, metal ions from the ‘soup’ of nuclear waste and fish out the 'bad' ones and leave the rest behind. This requires an understanding of chemical bonding and how the organic extractants bind to different metals. We can then exploit this knowledge to achieve separation by having them selectively bind to one type of metal and remove it from the soup.

There is mounting evidence that the molecules that are best at this contain soft donor atoms to the metals, so we need to understand soft donor-to-metal binding better. Arsenic is a soft donor, so we have prepared model complexes with it to understand the nature of the bonding. We might be able to use this new knowledge and understanding in a real system in the future.”

The research was carried out by an interdisciplinary team in the School of Chemistry and The Universities of Manchester and Regensburg and was funded and supported by the Royal Society, European Research Council, Engineering and Physical Sciences Research Council, and the National Nuclear Laboratory.